If you'd like to make these ahead and reheat later, I typically transfer to a ceramic casserole dish and bake covered for about 25 minutes at 400-450F (I put it in at the same time as cooking some Gardein stuffed turk'y, which is why it was that high). Bake until edges are golden, and you'll have the same, delicious fluffy mash (with a bit of delicious crust)